The virology core will provide vital support to all of the projects in this program and will additionally analyze the genetic sequences of strains of RV that differ in their in vitro and in vivo effects. This Core will be directed by Dr. David Schnurr, Ph.D., and Chief of the Viral Isolation Section of the Viral and Rickettsial Disease Laboratory (VRDL) of the California Department of Health Servic3s. The service functions of this laboratory are to act as a reference laboratory for other laboratories throughout California; to isolate and identify viruses from original specimens; to identify viruses by direct; and to test for antibodies by neutralization, ELISA or by indirect immunofluorescence. Direct detection of agents is by PCR, enzyme immuno-assay or by direct immunofluorescence. Dr. Schnurr's laboratory is thus skilled in the culture, direct detection and in serotyping methods necessary for the identification, titration, and characterization of viruses, including RV, in respiratory secretions from subjects in Project 2 and in samples of supernatant or cells in projects 1 and 3. This group will also characterize, maintain, titer, validate, maintain stocks, and provide RV16 and RV strains with variant phenotyping properties to the projects as needed. Virus preparations harvested in the course of experiments at the various projects will be submitted to the core for titration and often characterization. The core will perform neutralizing antibody assays on sera from potential human volunteers to screen for evidence of prior infection with a specific serotype of RV and for evidence of recent infection (seroconversion).